Unmanned Aircraft and Operation Method for the Same

ABSTRACT

An unmanned aircraft includes a propulsion system having a diesel or kerosene internal combustion engine and a charger device for engine charging. The propulsion system can be a hybrid propulsion system or a parallel hybrid propulsion system.

BACKGROUND AND SUMMARY OF THE INVENTION

Exemplary embodiment of the invention relate to an unmanned aircraft, aswell as to an operating method therefore.

An unmanned aircraft, also known as a drone or an unmanned aerialvehicle (UAV), is a flying apparatus for unmanned aviation that can beused, for example, for surveillance, exploration, or reconnaissance, asa target drone, for measurement purposes, or even equipped with weapons,especially in combat zones. Drones can be used, for example, formilitary, secret services, or civilian purposes. A flying drone isunmanned, either automated via a computer program or controlled from theground via radio signals or via satellite broadcasting. Depending on theapplication and equipment, drones can bear payloads, such as rockets fora military attack.

In the commonly used terminology, such aircraft are customarily referredto by the abbreviation UAV, which stands for an “unmanned aerialvehicle”. Another abbreviation, UAS, which stands for “unmanned aircraftsystem”, has also gained currency. The designation encompasses theentire system, constituted of the flying drone, the ground station fortakeoff and (where appropriate) landing, and the station for guidanceand supervision of the flight.

A comprehensive representation of UASs and different UAVs can be foundin Reg Austin's “Unmanned Aircraft Systems—UAVS design, development anddeployment”, published by Wiley in 2010. The present disclosure buildsupon the knowledge gained in that publication, and the document ishereby incorporated by reference.

German patent document DE 10 2010 021 022 A1 discloses a UAV in the formof a tiltwing aircraft.

UAVs with hybrid systems are known from patent documents U.S. Pat. No.8,128,019 B2 and EP 2 196 392 A2. These two documents relate tomini-UAVs, which can be brought by foot soldiers into the field and canfly with very low power at low altitude. In such a case, an internalcombustion engine is operated at a constant speed; an additionalelectric motor is variably operated in order to adjust the power in asimple and lightweight configuration.

Larger UAVs having a maximum takeoff weight from about 70 kg to about1,000 kg are currently operated solely with reciprocating engines, withwhich petrol engines are generally used. Even larger UAVs generally havegas turbine jet engines in order to be able to generate the requisitepower output.

The invention is aimed in particular at such larger UAVs having amaximum takeoff weight from about 70 kg, and exemplary embodiments aredirected to an unmanned flying apparatus having a low-cost propulsionthat also be used in a very versatile manner for different flightfunctions.

Exemplary embodiments of the invention are directed to an unmannedaircraft having a propulsion that comprises an internal combustionengine, configured as a diesel and/or kerosene engine, having a chargerdevice for engine charging.

Preferably, the propulsion is a hybrid propulsion which, in addition tothe internal combustion engine, comprises an electric motor and anenergy storage device for storing electric energy for driving theelectric motor.

Preferably the hybrid propulsion comprises a switchable coupling devicewith which the internal combustion engine and/or the electric motor canbe selectively connected to a thrust generator.

Preferably, the internal combustion engine and the electric motor can beselectively operated in parallel or in series.

Preferably, the charging device is designed for multi-stage chargingand/or comprises at least a first charger and a second charger, inparticular for multi-stage charging.

Preferably, the charging device comprises at least one charger that canbe driven by exhaust gas energy.

Preferably, the charging device comprises at least one mechanicalcharger.

Preferably, the at least one mechanical charger can be driven by anoutput shaft of the internal combustion engine and/or through anelectric motor.

Preferably, the mechanical charger can be driven by the electric motorof the hybrid propulsion.

Preferably, a controller is provided, with which the charger deviceand/or the hybrid propulsion can be controlled in accordance withvarious parameters in flight operation.

Preferably, the controller is designed in order to control the chargerdevice and/or the hybrid propulsion, in particular the switching on andoff of a first and/or second stage of the engine charging or theswitching on and off of the electric motor, in accordance with at leastone of the parameters of altitude, angle of a takeoff and/or landingflight to the vertical, desired velocity, allowable heat output,allowable operating noise level, and/or temperature.

Preferably, the internal combustion engine is a rotary piston engine.

Preferably, the aircraft has a maximum takeoff weight of more than 70kg, and in particular of more than 250 kg.

According to another aspect, the invention provides a method foroperating such an unmanned aircraft, the method involving controllingcharging of an internal combustion engine of a propulsion of the and/ora cooperation between an internal combustion engine and electric motorof a hybrid propulsion in accordance with at least one of the parametersof altitude, angle of a takeoff and/or landing flight to the vertical,desired velocity, allowable heat output, allowable operating noiselevel, and/or temperature.

Preferably, upon violation of a predetermined limit value for the atleast one parameter, then:

-   -   a first charging stage,    -   a second charging stage,    -   a mechanical charger,    -   an electric charger,    -   a first turbocharger,    -   a second turbocharger, or    -   an electric motor in addition to the running internal combustion        engine and/or    -   the internal combustion engine in addition to the running        electric motor    -   is switched on or switched off.

UAVs are used for various applications in various configurations, forboth military and civilian purposes. With regard to energy efficiency,it would be advantageous to have purely electric propulsion. Purelyelectric propulsion would also be advantageous especially in militaryoperations in terms of the thermal or acoustic signature. In otherwords, an electric propulsion has an advantage for UAVs in military usein that an especially quiet flight operation and/or a flight operationwith low thermal emission is possible, such that the risk of the UAVbeing detected is reduced.

Currently, however, purely electric propulsion is only suitable for lowpower and low flight times. For example, a purely electric propulsioncould be feasible for tactical UAVs with a maximum takeoff weight of upto about 70 kg in flight times between 20 minutes and at most threehours. Typical propulsion power would then be between 2 and 20 kW. Thereis then, however, a problem in the storage density of contemporarybatteries.

To be able to take advantage of an electric propulsion also for largerUAVs, and also for higher flight altitudes and longerdistances—especially for UAVs of the medium-altitude long-endurance(MALE) class, or the high-altitude long-endurance (HALE) class, theinvention provides for the use of internal combustion engines, which arediesel- or kerosene-drive and have a charging system.

Especially preferably, these internal combustion engines are a part of ahybrid propulsion; in particular, a diesel-electric hybrid propulsion isprovided.

Diesel and kerosene engines can be used universally, e.g., as propulsionfor maritime UAVs. The corresponding engines have a lower fuelconsumption than petrol engines or gas turbines, and also have a betterpartial load response.

For the purpose of optimizing energy and system technology, chargingthrough a charger device is provided according to the invention.

If the exhaust gas energy of the internal combustion engines is usedhere for charging, such as with the exhaust gas energy of dieselengines, then the thermal signature can thereby be considerably reduced.

Preferably, such a charged diesel or kerosene internal combustion engineis combined with electrical components in a power train for UAVs. Thisoffers, in particular, the following advantages:

For example, purely electric operation is possible in the emissionregion. The landing approach can be carried out using the internalcombustion engine, where a purely or mostly electric operation takesplace in the emission region in order to reduce the thermal and acousticsignature and thus increase the safety of the aircraft.

It is possible to have a boost operation by connecting an electric motorinto the mechanical drive train. Such a boost operation can be used, forexample, for the takeoff and/or landing phase in critical environmentalconditions, for escaping, or for other situations where unusually highpower is needed.

Such a propulsion can be used for all conceivable configurations of theUAV. The UAV can have, for example, a helicopter configuration, an A/Cconfiguration, a tiltwing configuration, and/or a tiltrotorconfiguration.

In particular, according to one embodiment of the invention, UAVs can bepropelled with propeller propulsion and/or impeller propulsion or withrotors of the performance class 30 kW to 400 kW per individual internalcombustion engine. At requisite higher power, it would be possible touse, for example, a plurality of internal combustion engines. It wouldbe particularly advantageous to take diesel/kerosene/rotary pistonengines into consideration.

Such a rotary piston engine is very compact and, even when used withdiesel or kerosene, is relatively lightweight. In addition, a rotarypiston engine can easily be used at a plurality of power stages. For alower power stage, it would be possible to use, for example, asingle-rotor rotary piston engine, while at high power levels, anotherrotor would come into use, and so forth.

A particularly preferred embodiment relates to the combination of onesuch internal combustion engine with one electrical motor and oneelectric energy storage device into a hybrid propulsion, which ispreferably provided as a parallel hybrid, meaning the provision ofvarious charging concepts for the internal combustion engine.

Preferably, a UAV is provided with “heavy fuel” fuel operation and withcharging. “Heavy fuel” refers in the USA in particular to diesel and/orkerosene propulsion.

Charged diesel engines are, of course, well known in the automotiveindustry. One example of a well-known charged diesel engine is thethree-cylinder turbodiesel “Smart” car engine, which is alsocommercially available as an individual engine. In the presentinvention, a charged diesel engine or a charged kerosene engine is usedfor an unmanned aircraft. This is of particular interest for maritimeapplications of UAVs.

The charging of the internal combustion engine is especiallyadvantageous. For example, charging is provided using the exhaust gasenergy. In particular, chargers coupled to exhaust gas turbines(“turbochargers”) are used here. In particular, use is made of theexhaust gas energy in two stages, through a series of connected exhaustgas turbines. Using the exhaust gas energy makes it possible to reducethe exhaust gas temperature. This lowers the signature for IR detectionof the UAVs.

Further advantages of engines operating with diesel or kerosene arebetter efficiency and better partial load response as compared to petrolengines or gas turbines; in addition, such engines are more durable.Diesel engines output their rated power at a lower rotational speed.

More preferably, at least one first charger and one second charger areprovided, in order to enable at least one two-stage charging.

The internal combustion engine can operate without charging for higheraltitudes and lower power. For slightly higher power, a first stage ofcharging is switched on. For even higher power, the second stage canthen be triggered. Of particular interest is two-stage charging withfurther usage of the exhaust gas energy. Such two-stage charging isinteresting for higher altitudes above around 4,000 m and can be usedeven at altitudes of about 10,000 m to 12,000 m.

Another interesting concept is the mechanical charging. It is thuspreferable for the internal combustion engine to comprise at least onemechanical charger as a charger. The advantage of mechanical charging isthat the motor does not need to work against the exhaust gas pressure.Preferably, the mechanical charging can be decoupled. The mechanicalcharger can be drive, for example, via a drive shaft of the internalcombustion engine and/or via an electric drive. The electric motor ofthe hybrid propulsion is particularly preferably used as the electricdrive.

Thus, it is conceivable to have multi-stage charging with or without theuse of exhaust gas energy, by the use of mechanical energy from theinternal combustion engine or from the electric drive.

It is particularly preferable to provide a controller which controls thedifferent manners of propulsion (electric motor and/or internalcombustion engine) and/or the different charging systems depending ondifferent parameters in flight operation of the UAV.

Possible parameters therefore are different altitudes. These can bedetected, for example, via a pressure sensor. In such an embodiment ofthe invention, the UAV comprises a pressure sensor producing signalsthat are used to control the propulsion. Other examples of possibleparameters are altitude and/or fast flight. Another parameter may be thepower for takeoff and/or landing operations. With such a propulsionconcept, both UAVs of the MALE class and UAVs of the HALE class can beoperated with great functional versatility and a wide range of possibleapplications.

According to another aspect, the invention provides a UAV having ahybrid propulsion in which the UAV is operated as a mobile power supplyunit after landing. The UAV preferably flies to the desired locationand, once there, is readily available, in contrast to ground-basedemergency generators. Through the increased application flexibility, theUAV can fly in particular to locations that are difficult or evenimpossible to reach by land and then ensure power there. The internalcombustion engine, which drives the generator to provide the desiredpower, serves as the primary energy supply. In another embodiment, theelectric energy storage device can be omitted so as to economize onweight. The UAV is as described above and below.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Embodiments of the invention shall be made more apparent below withreference to the accompanying drawings.

FIG. 1 illustrates a schematic representation of a first embodiment ofan unmanned aircraft with propulsion;

FIG. 2 illustrates a schematic representation of a second embodiment ofan unmanned aircraft with propulsion;

FIG. 3 illustrates a schematic representation of a third embodiment ofan aircraft with propulsion;

FIG. 4 illustrates a schematic representation of a first embodiment ofpropulsion for the unmanned aircraft according to FIGS. 1 to 3;

FIG. 5 illustrates a schematic representation of the first embodiment ofthe propulsion, in a first operating mode;

FIG. 6 illustrates a schematic representation of the first embodiment ofthe propulsion according to FIG. 4, in a second operating mode;

FIG. 7 illustrates a schematic representation of the first embodiment ofthe propulsion according to FIG. 4, in a third operating mode;

FIG. 8 illustrates a schematic representation of a second embodiment ofthe propulsion for one of the unmanned aircraft according to FIGS. 1 to3;

FIG. 9 illustrates a schematic representation of the second embodimentof the propulsion according to FIG. 8, in a first operating mode;

FIG. 10 illustrates a schematic representation of the second embodimentof the propulsion according to FIG. 8, in a second operating mode;

FIG. 11 illustrates a schematic representation of the second embodimentof the propulsion according to FIG. 8, in a third operating mode;

FIG. 12 illustrates a schematic representation of a third embodiment ofa propulsion for one of the unmanned aircraft according to FIGS. 1 to 3;

FIG. 13 illustrates a schematic representation of the third embodimentof the propulsion from FIG. 12, in a first operating mode;

FIG. 14 illustrates a schematic representation of the third embodimentof the propulsion from FIG. 12, in a second operating mode;

FIG. 15 illustrates a schematic representation of the third embodimentof the propulsion from FIG. 12, in a third operating mode;

FIG. 16 illustrates a schematic representation of the third embodimentof the propulsion from FIG. 12, in a fourth operating mode;

FIG. 17 illustrates a schematic representation of the third embodimentof the propulsion from FIG. 12, in a fifth operating mode; and

FIG. 18 illustrates a schematic diagram for representing a control ofthe propulsion of the unmanned aircraft on the basis of differentparameters in flight operation.

DETAILED DESCRIPTION

Three different embodiments of unmanned aircraft 10 are representedschematically, with a relevant propulsion 12, in FIGS. 1 to 3. Theunmanned aircraft 10 are also called drones or (in the technicalterminology) UAVs. They are a part of a system for unmannedaviation—called a UAS—with which military and civilian operations, andin particular reconnaissance flights, surveillance functions, ormeasurement functions, can be performed. Other than the depictedunmanned aircraft 12 , the UAS also has system components that are notshown here but are well known, such as, for example, the ground-basedcontrol station with which the UAV can be remotely operated, andcorresponding communication devices for communication between theunmanned aircraft 10 and the control station. For further details onUASs, reference can be made to the previously made publication, RegAustin's “Unmanned Aircraft Systems—UAS design, development anddeployment” published by Wiley in 2010.

FIG. 1 depicts a first UAV 14 which is provided in the form of anengine-operated glider having fixed wings 16, an ordinary empennage 18,and a thrust generator, here in the form of a propeller 20, e.g., on thevertical stabilizer 22. The construction of this first UAV 14 is basedon the construction of the glider “e-Genius”, provided with an electricauxiliary propulsion, which was developed by the University ofStuttgart's Institute of Aircraft Design and completed its maiden flighton 25 May 2011.

Unlike the known e-Genius touring motor glider with electric propulsion,the first UAV 14 is, in contrast, not equipped with a passenger cockpit;rather, the space that had been developed for the pilot and a passengeris provided in order to house UAS components and the payload thereof forperforming the desired UAV mission.

The second UAV 24 depicted in FIG. 2 is a helicopter version of a UAV,which can likewise be propelled with the propulsion 12. Here, a rotor 25or a rotor 25 and a tail rotor is/are provided as the thrust generator18.

The third UAV 26 depicted in FIG. 3 is another example of an unmannedaircraft 10, using the example of a tiltwing aircraft (a tiltwing andtiltrotor configuration). In this third UAV 26, the propulsion 12 isused to drive the thrust generator 18 in the form of tiltrotors 27.

Different embodiments for the propulsion 12 shall be made more apparentbelow with reference to FIGS. 4 to 17.

In all three of the different embodiments of the propulsion 12 depictedhere, the propulsion is provided with an internal combustion engine 28designed for diesel and/or kerosene operation and a charger device 30for charging the internal combustion engine 28.

The propulsion 12 is furthermore a hybrid propulsion 32 in all three ofthe embodiments depicted here. The hybrid propulsion 32 comprises anelectrical machine 23 in addition to the internal combustion engine 28.The electric machine 34 can be used as an electric motor 36 in one typeof operation, which is indicated by the letter M in the drawings, andcan be used as an electrical generator 38 in another type of operation,which is indicated by the letter G in the drawings. In additionalembodiments not depicted in greater detail here, the electrical machine34 may be either an electric motor or a generator. In furtherembodiments that shall be described in greater detail below, a separateelectric motor 36,M and a separate generator 38,G are provided.

The hybrid propulsion 32 further comprises an electric energy storagedevice 40, which is designed, for example, as an arrangement ofrechargeable battery cells or as an accumulator arrangement, and isidentified also with a “B” in the drawings. The electrical machine 34 isconnected to the electric energy storage device 40,B via powerelectronics 42.

In the illustrated embodiments, the hybrid propulsion 32 is configuredas a parallel hybrid, it being optionally possible to use the internalcombustion engine 28 or the electric motor 36 to propel the unmannedaircraft 10, or possible to use both the internal combustion engine 28and the electric motor together to propel the unmanned aircraft. To thisend, a shiftable coupling device 44 is provided, with which the internalcombustion engine 28 and the electrical machine 34 can selectively becoupled to an output shaft 62 connected to the thrust generator 18.

The shiftable coupling device 44 comprises a first coupling 46 forcoupling the internal combustion engine 28 and a second coupling 48 forcoupling the electrical machine 34. The coupling device 44 and thecharger device 30 can be controlled (see FIGS. 1 to 3) in accordancewith a variety of parameters during flight operation, as shall bedescribed in greater detail below. “Coupling” refers here to a generalterm for devices with which torque can be selectively transmitted (whenthe coupling is engaged) or shut down (when the coupling is disengaged).

As can be further seen in FIGS. 4 to 17, the charger device 30 comprisesat least a first charger 52 for charging the internal combustion engine28. The first charger 52 may be configured as an exhaust gasturbocharger 54 for making use of the exhaust gas energy for the purposeof charging.

In particular, the charger device 30 comprises a compressor 56 forgenerating pressure, in order to deliver combustion air at elevatedpressure to the internal combustion engine 28.

The compressor 56 can be coupled to a first exhaust gas turbine 58, soas to form the exhaust gas turbocharger 54 as the first charger 52.

The internal combustion engine 28 comprises a rotary piston engine 60,in a preferred design. The rotary piston engine 60 is in particularconfigured in such a manner as is described and illustrated in Germanpatent application DE 10 2012 101 032.3 , and is accordingly designedfor operation with diesel or kerosene. Depending on the desired powerlevel for the UA 14, 24, 26, the rotary piston engine 60 is configuredas a single-rotor rotary piston engine, a two-rotor rotary pistonengine, a three-rotor rotary piston engine, or a multi-rotor rotarypiston engine. The configuration of the rotary piston engine 60comprises a special ability for modularity, for this purpose, so thatone or a plurality of rotors can be provided at low cost.

Whereas the foregoing is a description the common elements of theembodiments of the propulsion 12 depicted here, the following addressesthe differences between the embodiments depicted here in greater detail.

FIGS. 4 to 7 illustrate a first embodiment for the propulsion 12, with asingle-stage charging, wherein only the first charger 52 is depicted, inthe form of the exhaust gas turbocharger 54 with the compressor 56,C andthe first exhaust gas turbine 58,T connected to the compressor 56. Theinternal combustion engine 28 and the electrical machine 34 canoptionally be connected to the output shaft 62 and thus to the thrustgenerator 18 via the first coupling 46 and the second coupling 48.

The propulsion 12 thus includes the internal combustion engine 28, whichmay be configured as a diesel engine and as a Wankel engine and isprovided with a charging system in the form of the charger device 30having the compressor 56 and the first exhaust gas turbine 58. Theengine output shaft 64 can be connected to the thrust generator 18 viathe first coupling 46. The generator 38 and the electric motor 36 or—asdepicted here—the electrical machine 34 able to operate as a generator Gor as an electric motor M are connected via an electronic controlunit—the power electronics 42,E—to a backup battery—the electric energystorage device 40,B—which is alternately charged during generatoroperation or is used to supply electrical energy to the electricalmachine 34 in electric motor operation.

FIG. 5 illustrates a first operating mode in which the hybrid propulsion32 is operated in pure electric operation. For this purpose, the firstcoupling 46 is disengaged and the second coupling 48 is engaged.

FIG. 6 illustrates the “conventional” operation, in which the propulsionpower of the hybrid propulsion 32 is provided solely through theinternal combustion engine 28. For this purpose, the first coupling 46is engaged and the second coupling 48 is disengaged.

In the third operating mode, illustrated in FIG. 7, both the firstcoupling 46 and the second coupling 48 are engaged, and thus both theinternal combustion engine 28 and the electrical machine 34 areconnected to the output shaft 62 and therefore also to one another. Inthis third mode, it is possible to perform an electric booster functionwhen the electrical machine is operating as the electric motor M—thusincreasing the system performance through additional electric energy—orto perform a charging operation during the generator function G of theelectrical machine 34.

Thus, through the illustrated configuration of the first embodiment ofthe hybrid propulsion 32, as depicted in FIGS. 4 to 7, at least the fourfollowing operating states are possible:

a) Conventional operation: The internal combustion engine 28 drives thethrust generator 18, while the generator G and the electric motor M aredecoupled. This corresponds to the operating mode of existing UAVpropulsion systems based on internal combustion engines.

b) “Electric boost”: In addition to the internal combustion engine 28,the electric motor M is also coupled to the output shaft 62. This makesit possible to transmit an additional torque to the output shaft 62,thus making additional power available for a brief time—depending on thecapacity of the electric energy storage device 40—and accordinglyenabling compensation for peaks in the power demand.

c) “Charging mode”: In operating phases which do not require the entireengine power of the internal combustion engine 28 for the thrustgenerator 18, a portion of the available power can be delivered to thegenerator G, in order to re-charge the electric energy storage device40.

d) “Purely electric operation”: In addition to the operating modesabove, the internal combustion engine 28 can also be decoupled andturned off, in order to switch to a purely electric operation. Here, theelectric motor E is then coupled to the output shaft, which is suppliedwith electric energy from the electric energy storage device B.

This offers, in particular, the following advantages:

The function of a parallel hybrid allows for purely electric operationto reduce the thermal and acoustic signature in critical mission phases.At the same time, in conventional operation the high energy storagedensity of fossil fuels can be exploited, in order to achieve rangesthat are not available through pure electric propulsion. In addition,the system offers the possibility of charging batteries in flight,whereby an efficient operating state of the internal combustion engine28 can be selected through a load point increase of the internalcombustion engine 28.

FIGS. 8 to 11 illustrate a second embodiment of the hybrid propulsion32. This second embodiment corresponds essentially to the firstembodiment except for the difference that in addition to the firstexhaust gas turbine 58, the second embodiment also comprises a secondexhaust gas turbine 66,T, which is or can be coupled to the engineoutput shaft 64 and/or the output shaft 62.

The second exhaust gas turbine 66 makes it possible for the exhaust gasenergy of the internal combustion engine 28 to be exploited in twostages. In the first exhaust gas turbine 58,T, the exhaust gas energy isused by the compressor 56,C for charging the internal combustion engine28. In the second exhaust gas turbine 66, the remaining exhaust gasenergy is used for further propulsion.

This makes it possible, in contrast to the first embodiment, to lowerthe exhaust gas temperature and thus reduce the thermal signature of theunmanned aircraft 10.

The functionality of the second embodiment of the hybrid propulsion asillustrated in FIGS. 8 to 11 otherwise corresponds to that of the firstembodiment of the hybrid propulsion 32, as illustrated in FIGS. 4 to 7.Accordingly, FIG. 9 illustrates the first operating mode for the pureelectric operation, FIG. 10 illustrates the second operating mode forthe conventional operation, and FIG. 11 illustrates the third operatingmode in which either the electric boost can be performed or the chargingoperation can be performed. For further details of these three operatingmodes, reference is made to the above implementations with respect tothe first embodiment.

FIGS. 12 to 17 illustrate a third embodiment of the hybrid propulsion32, as an example of the propulsion 12 for the UAVs 14, 24, 26, whereinidentical or corresponding elements bear identical reference numerals asin the first two embodiments and reference can be made to the abovestatements for further details.

In this third embodiment, the charger device 30 is configured forswitchable multi-stage charging and comprises the first charger 52 and asecond charger 70 for providing the multi-stage charging, wherein thedifferent chargers 52, 70 can be switched on or switched off under thecontrol of the controller 50 in order to switch the different stages ofcharging on or off.

In the third embodiment of the hybrid propulsion 32, at least oneelectric motor 36,M and one generator 38,G are represented here in placeof the electrical machine 34, which can operate in both the electricmotor operation and the generator operation. The coupling device 44comprises the first coupling 46 for coupling the engine output shaft 64to the output shaft 62, the second coupling 48 for coupling the electricmotor 36,M to the output shaft 62, and a third coupling 72 for couplingthe generator 72 to the engine output shaft 64.

Furthermore, a charger coupling device 74 is provided, in order toswitch the charger device 30, and in particular to couple or decouplethe first charger 52 and/or the second charger 70.

The compressor 56 having the first exhaust gas turbine 58 is provided inorder to form the first charger 52.

Next, a mechanical charger 76 is provided as the second charger 70. Themechanical charger 76 may use, for example, the compressor 56 and amechanical propulsion source. For this purpose, a first design or firstcharging mode makes use of an electric propulsion and in particular theelectric motor 36,M. A second implementation or second charging modemakes use of the movement of the engine output shaft 64 for thispurpose.

In the embodiment illustrated in FIG. 12, schematically, the compressor56,C is represented as a pressure generator that can be coupled to thefirst exhaust gas turbine 58 through a first charger coupling 78 of thecharger coupling device 74 in order to form the exhaust gas turbocharger54 as a first charger 52, and can be coupled to the electric motor 36,Mthrough a second charger coupling 80 of the charger coupling device 74in order to form the electrically operated mechanical charger 76 and, ifnecessary, can be coupled to the engine output shaft 64 through a thirdcharger coupling 82 of the charger coupling device in order to form themechanical charger 76 that can be driven by the movement of the outputshaft.

In the implementation depicted, simply the second coupling 48 of theswitchable coupling device 44 is indicated as the third charger coupling82.

FIGS. 13 to 17 depict five different operating modes for this thirdembodiment of the hybrid propulsion 32. In the operating mode of FIG.13, the first charger coupling 78 is engaged such that the firstcharging stage is active. The internal combustion engine 28, beingcharged with the first stage, is connected to the thrust generator 18through the engaged first coupling 46. The generator 38,G is connected,as necessary, to the engine output shaft 64 through the engaged thirdcoupling 72. Therefore, the first operating mode illustrated in FIG. 13corresponds to charging operation, where thrust is produced via theinternal combustion engine 28 being charged on the first stage, andexcess power is used to charge the electric energy storage device 40.The second coupling 48 and the second charger coupling 80 are disengagedsuch that the electric motor 36 is connected neither to the chargerdevice 30 nor to the thrust generator 18.

FIG. 14 illustrates the electric operation, as the second operatingmode. For this purpose, the second charger coupling 80 is disengaged andthe electric motor is connected through engagement of the secondcoupling 48 to the output shaft 62 and therefore the thrust generator18. The first coupling 46 and the third coupling 72 are disengaged suchthat neither the internal combustion engine 28 nor the generator isconnected to the output shaft 62. The internal combustion engine 28 canbe switched off here.

The third operating mode illustrated in FIG. 15 corresponds to theconventional operation in single-stage charging, purely with the exhaustgas turbocharger 54. For this purpose solely the first coupling 56 andthe first charger coupling 78 are engaged, and all other couplings aredisengaged.

FIG. 16 illustrates a fourth operating mode in the form of an operationpurely with the internal combustion engine 28, which is instead chargedby the second charger 70 (electric charging). For this purpose, thefirst coupling 46 and the second charger coupling 80 are engaged and allother couplings are disengaged.

FIG. 17 illustrates a fifth operating mode in which the electric boostis presented as an additional functionality. For this purpose, theinternal combustion engine 28 (the exhaust gas turbocharger 54 beingactive) having undergone single-stage charging is connected to thethrust generator 18; in addition, the electric motor 36 is stillconnected to the thrust generator 18, as well. The first coupling 46 andthe second coupling 48 as well as the first charger coupling 78 areengaged, and all other couplings are disengaged.

It shall be readily understood that other operating modes are possiblethrough various switches made with the various couplings 46, 48, 72, 78,80, 82.

In the third embodiment of the hybrid propulsion 32 illustrated in FIGS.12 to 17, the propulsion 12 has an internal combustion engine (a dieselengine/Wankel engine) having a charging system (charger device 30)comprising the compressor 56 and the exhaust gas turbine 58. Thecompressor 56 of the charger device 30 can, in this case, be propelledvia a coupling system (charger coupling device 74) either by the exhaustgas turbine 58 or an electric motor, e.g., the electric motor M of thehybrid system. The engine output shaft 64 of the internal combustionengine 28 can be directly connected to the thrust generator 18 (e.g., apropeller 20 or rotor 25, 27). In addition, the electrical generator38,G is to be connected to the engine output shaft 64 and/or the outputshaft 62 via a separate coupling (third coupling 72). The generator 38,Gand the electric motor 36,M are connected via an electronic control unit(power electronics 42,E) to a backup battery (an example of the electricenergy storage device 40,B) which alternately is charged by thegenerator 38,G or is to be used for supply to the electric motor 36,M.

The construction illustrated in FIGS. 12 to 17 enables, in particular,the following four operating states:

a) “Conventional operation”: The compressor 56 of the exhaust gasturbocharger 54 is propelled by the exhaust gas turbine 58 of thecharger device 30, while the electric motor 36,M and generator 38,G aredecoupled. This corresponds to the operating mode of existingconventional propulsion systems, but with the difference of diesel orkerosene operation with additional charging.

b) “Electric turbo”: The compressor 56 of the charger device 70 is inthis case propelled by the electric motor 36,M. This allows a greaterincrease in power to be generated than would take place in coupling ofthe electric motor 36,M to the output shaft 62.

c) “Electric boost”: Here, in addition to the power of the internalcombustion machine, the power of the electric motor 36,M is alsotransmitted to the output shaft 62.

d) “Charging mode”: In operation phases where not all of the enginepower of the internal combustion engine 28 is required by the thrustgenerator 18, then a portion of the available power can be delivered tothe generator 38,G, in order to re-charge the battery (electric energystorage device 40,B). The compressor 56 of the charger device 30 is inthis case driven by the exhaust gas turbine 58 while the electric motor36,M is decoupled.

This offers, in particular, the following advantages.

In addition to the functionality of a parallel hybrid (operation with aninternal combustion machine, purely electric operation, or recharging ofthe battery), the electric motor 36,M can be used in two ways in orderto make additional power available:

a) through an electric boost in which the power is directly fed to theoutput shaft 62, or

b) through an electrically driven mechanical charger 76, with which therequired power for charging is provided by the electric motor 36,M andneed not interfere with the process of the internal combustion engine.This is advantageous in that, in contrast to propulsion with an exhaustgas turbine 58, no back pressure is built up in the exhaust gas, againstwhich the internal combustion engine 28 would otherwise need to work. Incontrast to the use of a mechanical propulsion for the mechanicalcharger 76—in particular, through coupling to the engine output shaft64—there is no need to detract any mechanical power of the output shaft.

Different embodiments of the hybrid propulsion 32 are presented above,with reference to the drawings. It shall be readily understood thatfurther embodiments are also possible, but these are not shown here. Forexample, the second exhaust gas turbine 66 may also be present in theembodiment illustrated in FIGS. 12 to 17, and in particular may beswitchable via a separate switching device that can switch this secondexhaust gas turbine 66 on or off.

Furthermore, either in addition to or alternatively to the propulsion ofthe mechanical charger 76 through the electric motor 36 of the hybridpropulsion, it would also be possible to have a separate electric motorfor the propulsion of the compressor. On the other hand, it would alsobe possible to drive the compressor 56 via the engine output shaft 64.Moreover, instead of the depiction with only one compressor 56, it wouldalso be possible to provide a plurality of compressors, which can bedriven via the first exhaust gas turbine 58, the second exhaust gasturbine 66, the electric motor 36 of the hybrid propulsion 32, and/orthrough the engine output shaft 64.

A possible control of the hybrid propulsion 32 for the unmanned aircraft10 shall be described in further detail below, with reference to theillustration in FIG. 18.

As illustrated in FIGS. 2 and 3, the unmanned aircraft 10 may be a UAV24, 26, which is capable of vertical takeoff and landing (VTOL), and/ora UAV 14, 26, which is capable of a convention takeoff and landing aswith an airplane (making use of the flow of air during travel of theaircraft 10 (CTOL)).

The diagram in FIG. 18 illustrates the required power P over the flightvelocity v. The arrow R indicates the range of cruising flight—thecruising range. “ISA” stands for the international standard atmosphere.

The curve S shows the power needed for various flight conditions at sealevel and at standard atmospheric conditions; the curve H1 shows thepower needed at high altitudes and standard atmospheric conditions, andthe curve H2 shows the power needed at higher altitudes and at standardatmospheric conditions elevated by approximately 15° C.

The various operating modes provide coverage for all of the power rangesthat are required with these various operating conditions and flightconditions.

The controller switches through the various operating modes, inparticular the switching on or off of the charger device or theswitching on or off of various chargers or various stages of charging,in accordance with parameters that are indicative of these operatingconditions, such as the target/actual velocity, altitude (in particular,as can be detected via pressure sensors), desired VTOL or CTOL, ortemperature.

The power stages L represented in the drawings, which can be switched onor off by the control, denote the maximum available power for:

L1 internal combustion engine operation without charging;

L2 internal combustion engine operation with charging in a firststage—in particular, operation of the first charger 52, i.e., of theexhaust gas turbocharger 54;

L3 internal combustion engine operation with charging in the secondstage—for example, operation of the second charger 70, such as inparticular of the electrically drive mechanical charger 76;

L4 internal combustion engine operation with charging in the secondstage and additionally with the electric boost function.

The engine charging increases the available engine power of the internalcombustion engine 28. This allows in particular for vertical takeoffs athigher altitudes and/or at higher ambient temperatures (‘hot and highconditions”). This further increases the maximum cruising velocity.

The possibility of the electric boost further increases the availablepower for such conditions, where the limit of the power increase isreached through engine charging. This makes it possible to furtherextend the application areas. For example, vertical takeoffs at evenhigher altitudes and at even higher temperatures are possible; a maximalcruising velocity in difficult conditions can also be further increased.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

REFERENCE SIGNS LIST

-   10: unmanned aircraft;-   12: propulsion;-   14: first UAV;-   16: wing;-   18: thrust generator;-   20: propeller;-   22: vertical stabilizer;-   24: second UAV;-   25: rotor;-   26: third UAV;-   27: tiltrotor;-   28: internal combustion engine;-   30: charger device;-   32: hybrid propulsion;-   34: electrical machine;-   36,M: electric motor;-   38,G: generator;-   40,B: electric energy storage device;-   42,E: power electronics;-   44: switchable coupling device;-   46: first coupling;-   48: second coupling;-   50: controller;-   52: first charger;-   54: exhaust gas turbocharger;-   56: compressor;-   58: first exhaust gas turbine;-   60: rotary piston engine;-   62: output shaft;-   64: engine output shaft;-   66: second exhaust gas turbine;-   70: second charger;-   72: third coupling;-   74: charger coupling device;-   76: mechanical charger;-   78: first charger coupling;-   80: second charger coupling;-   82: third charger coupling;-   S: sea level;-   R: cruising range;-   v: forward speed;-   P: power;-   H1: high altitude, at ISA;-   H2: high altitude, at ISA+15° C.;-   ISA: standard atmosphere;-   VTOL: vertical takeoff/landing;-   CTOL: conventional takeoff/landing;-   L1: internal combustion engine operation without charging;-   L2: internal combustion engine operation with charging, first stage;-   L3: internal combustion engine operation with charging, second    stage;-   L4: internal combustion engine operation with charging, second    stage+electric boost

1-15. (canceled)
 16. An unmanned aircraft, comprising: a propulsionsystem that comprises a diesel or kerosene internal combustion engine;and a charging device configured to charge the internal combustionengine of the unmanned aircraft.
 17. The unmanned aircraft of claim 16,wherein the propulsion system is a hybrid propulsion system which, inaddition to the internal combustion engine, comprises an electric motorand an energy storage device configured to store electric energy fordriving the electric motor.
 18. The unmanned aircraft of claim 17,wherein the hybrid propulsion system comprises a switchable couplingdevice with which the internal combustion engine or the electric motorcan be selectively connected to a thrust generator.
 19. The unmannedaircraft of claim 17, wherein the internal combustion engine and theelectric motor are configured to be selectively operated in parallel orin series.
 20. The unmanned aircraft of claim 16, wherein the chargingdevice is configured for multi-stage charging or comprises at least afirst charger and a second charge for multi-stage charging.
 21. Theunmanned aircraft of claim 16, wherein the charging device comprises atleast one charger that is configured to be driven by exhaust gas energy.22. The unmanned aircraft of claim 16, wherein the charging devicecomprises at least one mechanical charger.
 23. The unmanned aircraft ofclaim 22, wherein the at least one mechanical charger is driven by anoutput shaft of the internal combustion engine or through an electricmotor.
 24. The unmanned aircraft of claim 23, wherein the propulsionsystem is a hybrid propulsion system which, in addition to the internalcombustion engine, comprises an electric motor and an energy storagedevice configured to store electric energy for driving the electricmotor, and the mechanical charger is configured to be driveable by theelectric motor of the hybrid propulsion.
 25. The unmanned aircraft ofclaim 17, further comprising: a controller configured to control thecharging device or the hybrid propulsion in accordance with variousparameters in flight operation.
 26. The unmanned aircraft of claim 25,wherein the controller is configured to control switching on and off ofa first or second stage of the engine charging or the switching on andoff of the electric motor, in accordance with at least one of theparameters of altitude, angle of a takeoff or landing flight to thevertical, desired velocity, allowable heat output, allowable operatingnoise level, or temperature.
 27. The unmanned aircraft of claim 16,wherein the internal combustion engine is a rotary piston engine. 28.The unmanned aircraft of claim 16, wherein the aircraft has a maximumtakeoff weight of more than 250 kg.
 29. A method for operating anunmanned aircraft, the method comprising: controlling charging of aninternal combustion engine of a propulsion system of the unmannedaircraft or a cooperation between an internal combustion engine andelectric motor of a hybrid propulsion in accordance with at least one ofthe parameters of altitude, angle of a takeoff or landing flight to thevertical, desired velocity, allowable heat output, allowable operatingnoise level, or temperature.
 30. The method of claim 29, wherein uponviolation of a predetermined limit value for the at least one parameter,then the method comprises switching on or off: a first charging stage; asecond charging stage, a mechanical charger, an electric charger, afirst turbocharger, a second turbocharger, an electric motor in additionto the running internal combustion engine, or the internal combustionengine in addition to the running electric motor.